Read your grass seed label

Identify the bag and the job

Put the bag beside you. Photograph its directions and seed-analysis tag, including the lot identification and test date if shown. Record the exact product, bag weight and whether the directions are for a new lawn, a bare repair or overseeding. A product name by itself does not identify the instructions on your bag.

Choose one calculation basis

The distinction is dimensional: a product rate already specifies the material to spread. Dividing that material again by its PLS fraction changes the instruction. The PLS conversion is useful when the starting target is explicitly expressed as PLS. LSU AgCenter's method starts with that kind of target and converts it into a required bag-material weight. LSU: Pure Live Seed Calculation

Hypothetical product-rate example: a 2,400-square-foot overseeding job uses directions of 4 pounds of packaged product per 1,000 square feet. The calculated material is 2,400 ÷ 1,000 × 4 = 9.6 pounds. If a matching 8-pound bag is sold, purchasing whole bags means two bags, not spreading all 16 pounds. You still follow the product rate. These figures demonstrate the arithmetic and are not a rate recommendation.

Read the analysis rows as quantities with different meanings

The pure-seed percentage describes the seed component's share by weight. The germination percentage describes its test result, not another share of the bag. USDA distinguishes physical-purity analysis from germination testing, which is performed under favorable test conditions; it separately describes tests of vigor and viability. A germination figure is not a measured emergence rate for your yard. USDA Seed Testing Program

For a single component, the basic fraction is:

PLS fraction = (pure-seed % ÷ 100) × (germination % ÷ 100).

For a mixture or blend whose component pure-seed percentages are expressed as percentages of the whole bag material, calculate each row and add:

PLS fraction = Σ[(component pure-seed % ÷ 100) × (that component's germination % ÷ 100)].

LSU's mixture method sums those row contributions. Do not multiply by a second “mixture share” when the component percentage is already its whole-bag share. If the label gives a different basis or you cannot establish the basis, stop and clarify it. LSU: mixture and blend method

Work a complete, invented mixture

This teaching tag is hypothetical. It is not a product label or a recommended mixture. Assume the remaining 10% is inert material, there are no other seed components and no separately reported hard or dormant seed.

A 10-pound bag in this example has 10 × 0.775 = 7.75 pounds of calculated PLS. The 90% and 80% germination results are not added together. Grass A's 55% is not applied twice.

Now suppose a separate, applicable recommendation explicitly calls for 2 pounds PLS per 1,000 square feet over 2,000 square feet. That hypothetical target is 4 pounds PLS. Required bag material is 4 ÷ 0.775 = 5.161290… pounds. Retain the full fraction in the calculation and show a sensible approximate result. Whole-bag purchasing is a later rounding decision. Do not round 0.775 down to 0.77 midway through the work.

The example explains a conversion. It does not establish that 2 pounds PLS is appropriate for any Minnesota species, task or site.

Stop when hard or dormant seed needs interpretation

If your tag separately reports hard seed or dormant seed, this site's first-version simplified PLS calculation does not support that case. Do not silently omit those values, and do not automatically add them to germination. USDA's seed-analysis explanation treats them as separate categories; the appropriate calculation needs the seed type, report definitions and target recommendation. Ask the supplier, seed-testing laboratory or local Extension how to interpret the complete tag. USDA: Seed Report of Analysis and Labeling, printed pages 12–13

Unreadable or missing information is also unresolved information. Do not substitute a familiar pair such as 98% purity and 85% germination for the lot you bought. Example values are not measurements of your bag.

Why an online package can disagree with another version

On November 7, 2026, Pennington's Smart Seed Dense Shade product webpage listed 8 pounds per 1,000 square feet for new lawns and 4 for overseeding. A retailer-hosted package PDF listed 12 for new lawns and 4 for overseeding. The PDF also used “up to 56% coating material.” Current manufacturer page, retailer-hosted package PDF, page 1

That establishes a difference between the two accessed documents. It does not establish which formulation or package revision you own, or that a current lot is mislabeled. Use the directions and analysis applicable to your exact bag; ask the manufacturer to resolve a material conflict before spreading. This site does not supply a default rate for that brand.

“Up to” is a limit statement, not an actual batch analysis. In particular, subtracting 56 from 100 does not prove that a bag has 44% pure seed: the actual coating quantity and the remaining analysis are not established by that phrase. Keep coverage directions, coating claims and the lot-analysis tag separate.

Cost per calculated PLS is one comparison, not a winner

For a supported, complete tag, bag price ÷ (bag weight × PLS fraction) gives cost per pound of calculated PLS. In a hypothetical comparison, a $32, 10-pound bag at 0.775 costs about $4.13 per calculated PLS pound. A $28, 10-pound bag at 0.60 costs about $4.67. These are invented prices and fractions, not current offers.

The lower number only wins that narrow arithmetic comparison. It does not prove suitable species or cultivars, field establishment, shade or traffic fit, irrigation needs or the best overall purchase. Different seed sizes also mean equal weights are not equal seed counts. Use the analysis to understand what you are buying, then check suitability and the site-preparation plan before deciding.

Leave with an auditable input sheet

Keep area; job type; exact bag/lot; rate source; rate basis; bag weight; analysis rows; unresolved fields together. If the basis is packaged product or stated coverage, use that path directly. If it is PLS, check the complete supported inputs before converting. If you cannot resolve the basis or a special seed category, the useful result is an explanation of what to clarify, not a fabricated bag count.

Sources and limits

Accessed 2026-11-07, Asia/Shanghai. No bag was sampled or laboratory-tested by this site.